1. Field of the Invention
The present invention relates to a cassette-type image taking apparatus and a radiographic apparatus.
2. Related Background Art
Methods by which an object is irradiated with a radiation, the intensity distribution of the radiation transmitted by the object is detected and a radiograph of the object is obtained are extensively used in industrial nondestructive tests and medical diagnoses.
In recent years, there have been developed digital radiographic apparatuses each using a radiation detector composed by stacking two-dimensional array sensors in which optical detection elements, consisting of minute photoelectric conversion elements, switching elements and the like, are arranged in a grid form and a scintillator for converting a radiation into visible light. The digital radiographic apparatus converts a radiation transmitted by an object into visible light with the scintillator, and detects this visible light as an electric signal with the photoelectric converting portions of the optical detection elements. This electric signal, after being read out from each optical detection element by a prescribed reading method, undergoes analog-to-digital (A/D) conversion, resulting in a digital radiographic signal. This radiographic signal, after undergoing signal processing in various ways by an image processing device downstream, is reproduced (visualized) by reproducing means such as a CRT into a radiographic image.
Such a digital radiographic apparatus is broader in the range of radioactive dose (dynamic range) that can be detected than a radiographic apparatus using a silver salt film and a fluorescent screen (or sensitized paper), and has a another advantage of being able to instantaneously provide a processed visible image because an image signal converted into an electric signal can be immediately obtained. Furthermore, the digital image data that have been obtained can be transferred by wire or wireless means to a system control unit, a storage server or the like to be readily incorporated into a database.
Incidentally, there are two types of radiographic apparatuses for taking still pictures for medical use, the console type and the portable type, of which one or the other can be selected according to the applicable to the patient to be diagnosed. The console type usually has, underneath a table on which the patient is laid, an image taking apparatus containing film or a photoelectric converter, and irradiates the patient with a radiation emitted from the above to acquire a radiographic image (for instance, an abdominal image). The portable type is used when the patient is so seriously ill to be brought to the table under which the image taking apparatus is installed or when a specific photographic method is used which is incompatible with the console type. In such a case, a portable image taking apparatus (known as a cassette) is inserted under the patient's body, which is irradiated with a radiation from above to obtain a radiographic image. Especially in the former case, the portable type radiographic apparatus has to be brought to where the patient is, it is desirable for the apparatus to be minimized in size and weight to improve its portability and operating ease.
However, for a portable digital radiographic apparatus; an electronic cassette is more difficult to be reduced in size and weight than a film cassette because an electronic cassette or a cassette-type image taking apparatus has to be mounted with many constituent elements needed for outputting a radiographic image as a digital image data, such as a two-dimensional array sensor and an A/D converter circuit. Moreover, if cables for power supply and data transmission are eliminated and data are transmitted wirelessly, a memory for temporary storage of digital image data and a power source unit (battery) for supplying power to the electronic cassette will be additionally needed, making it even more difficult to reduce the size and weight.
Therefore, following consideration of portability and operating ease, it has been proposed to use electronic cassette, while making best efforts to reduce the size and weight of an electronic cassette which would use cables for power supply and/or data transmission, to make the cables detachable and connect them only when, for instance, an image is picked up and data are transmitted.
FIG. 10 is a schematic diagram illustrating a portable digital radiographic apparatus 1000 according to the prior art. The radiographic apparatus 1000 is configured by connecting via a cable 1300 an electronic cassette 1100 which converts into digital image data a radiation transmitted by a patient P, which is the object, and a control unit 1200 which transmits a control signal for driving the electronic cassette 1100 and receives digital image data from the electronic cassette 1100. A power supply unit 1400 for supplying power to the cassette is also connected by the cable 1300.
In using the radiographic apparatus 1000, the electronic cassette 1100 in a state of not being connected to the cable 1300 is, for instance, inserted between the patient P and a bed 1500 as shown in FIG. 11 and arranged in a region suitable for image pickup. FIG. 11 here is a sketchy diagram showing an example of arrangement of the electronic cassette 1100. Upon completion of arranging the electronic cassette 1100, the cable 1300 is connected to a connecting port 1110 of the electronic cassette 1100 to establish connection among the electronic cassette 1100, the control unit 1200 and the power supply unit 1400. Then, receiving control signals from the control unit 1200 and power from the power supply unit 1400 via the cable 1300, the electronic cassette 1100 begins to operate and picks up an image. After the image is picked up, digital image data are transmitted from the electronic cassette 1100 to the control unit 1200 via the cable 1300.
However, if the operator, when arranging the electronic cassette 1100 to which the cable 1300 is not yet connected, arranges the electronic cassette 1100 without paying attention to its connecting port 1110, the state illustrated in FIG. 12 may arise. FIG. 12 here is a sketchy diagram showing one example of case in which the connecting port 1110 of the electronic cassette 1100 is positioned between the patient P and the bed 1500. As a result, in order to connect the cable 1300 to the connecting port 1110 of the electronic cassette 1100, the operator will have to raise the body of the patient P and connect the cable 1300 to the connecting port 1110 or once pull out the electronic cassette 1100, change is direction, again insert it between the patient P and the bed 1500, and connect the cable 1300 to the connecting port 1110. In either case, the patient P will be forced to change his or her bodily posture.
The detection area of the radiation detector of the electronic cassette 1100 may be shaped in a 17″×15″ rectangle, for instance, to match the size of a commercially available film or film cassette. In this case, conceivably, the electronic cassette 1100 may be arranged as illustrated in FIGS. 13A and 13B. FIGS. 13A and 13B here are sketchy diagrams illustrating examples of arrangement of the electronic cassette 1100. FIG. 13A shows a case in which the connecting port 1110 of the electronic cassette 1100 is not positioned between the patient P and the bed 1500, while FIG. 13B shows a case in which the connecting port 1110 of the electronic cassette 1100 is positioned between the patient P and the bed 1500.
However, if the connecting port 1110 of the electronic cassette 1100 is positioned between the patient P and the bed 1500 as shown in FIG. 13B, the patient P will be forced to change his or her posture as described above when the cable 1300 is connected to the connecting port 1110.
Also, as an electronic cassette may be used in many different positions with a patient whose bodily movement is strictly limited, the operator is imposed by the trouble of having to pay particular attention to the position of the connecting port of the electronic cassette in arranging the electronic cassette.
Therefore, it is desirable for the operator to be able to easily connect the cable to the electronic cassette and for the patient not to be obliged to change his or her posture for the convenience of cable connection to the electronic cassette.